To produce a steel wire strand, steel billets are heated to red heat or higher and hot rolled in a rod mill. The elevated temperature of the processing causes the formation of iron oxides on the surface of the hot-rolled rod (designated herein as "strand"). These iron oxides, such as FeO, Fe.sub.2 O.sub.3, and Fe.sub.3 O.sub.4 are known as mill scale. Elevated temperature heat-treating of steel strand may also cause such scale to form.
Mill scale levels vary depending on the type of rod rolling mill used, the level of elevated temperature reached, and the time at elevated temperature. Traditional rod mills will produce rod with approximately one (1) percent by weight of mill scale. In a newer process for rod production, the hot-rolled rod is control-cooled thereby reducing mill scale levels to approximately 0.25 to 0.50 percent by weight. During the transit and storage of steel rod additional iron oxides form, commonly known as rust.
For the successful production of steel wire or strand from hot-rolled or heat-treated steel rod, the iron oxides on the rod must first be removed essentially in their entirety.
Iron oxide scale removal from hot-rolled or heat-treated steel rods can be accomplished using chemical or mechanical processing. Chemical processing includes such methods as acid pickling and molten salt bath immersion. Mechanical processing includes such methods as abrasive belting, shot blasting, and reverse bending. Reverse bend descaling is based on the fact that steel is ductile and mill scale is brittle. Controlled deformation of the steel rod therefore loosens and removes the brittle mill scale. One method of controlled deformation is reverse bending as by passing rod over a series of sheaves.
These scale removal methods are as described in Stalson U.S. Pat. Nos. 3,496,086 and Stalson 3,044,098 and the following publications:
Stalson, Stanley L., "An Overview of Mechanical Descaling," Joint Conference Proceedings, Ferrous Division/Pacific Coast Meeting, The Wire Association International, Inc., Guilford, Connecticut 06437, May 19, 1977, pps. 63-90 PA1 STEEL WIRE HANDBOOK, Vol. 1, The Wire Association Inc., Stamford, Connecticut, 1965, "Cleaning and Coating in Preparation for Drawing," Chapter 3, pps. 93-229
This invention relates to the removal of iron oxide scale dust that remains on steel rods and strands after descaling by mechanical processing methods. The scale dust is attached to the steel strand as by electromagnetic or elastrostatic forces. This abrasive residual iron oxide dust must be removed to maximize wire drawing die life and productivity. To clean steel rod in preparation for drawing, the rod is passed through the apparatus. The apparatus removes residual dust by breaking the forces attaching the dust to the steel strand using equal, opposing high-velocity multiple air jets situated at each end of the apparatus. The apparatus is further designed to contain and to collect the removed dust thereby preventing dispersion into the atmosphere. The apparatus also continuously processes the dust-laden air, separating the scale dust and returning only clean air to the atmosphere.